Separate SHA224 from SHA256 config options.

These options are still dependant on each other.
This is an intermediate step.

Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
diff --git a/configs/config-thread.h b/configs/config-thread.h
index 47dd5e2..1deb8a5 100644
--- a/configs/config-thread.h
+++ b/configs/config-thread.h
@@ -68,6 +68,7 @@
 #define MBEDTLS_PK_C
 #define MBEDTLS_PK_PARSE_C
 #define MBEDTLS_SHA256_C
+#define MBEDTLS_SHA224_C
 #define MBEDTLS_SSL_COOKIE_C
 #define MBEDTLS_SSL_CLI_C
 #define MBEDTLS_SSL_SRV_C